Can anyone confirm wether or not, on an AWD car, if you replace one tire, that you need to replace them all? Ive been told that the difference in tire diameter ruins the tranny and diff and other assorted parts. But wouldn't driving in slippery conditions do the same, since the wheels would also be spinning at differnent speeds?

 

Ive heard that if there is more than like 2/32 difference in tread you will damage your awd system. Never had any proof either way, but i heard this from a guy at a tire shop, said an sti had major problems, and my dealer. Never experienced it for myself though..

 

you could get away with it, but yes technically when you blow one you should replace all 4

 

It shouldn't damage your AWD system at least not to quattro. The quattro should automatically adjust the power distribute to the wheel based on the condition. But, like R.A.I. stated, technically you should replace all 4. If not, try replace a pair.

 

No driven wheels on any car should have mismatched tire diameter. AWD or not. If you have to replace just one, try looking for the same diameter. But if the rest are worn out just get a whole new set.
I paid for a set of Falken 512 for about $600 with everything with road hazard included at discount tires. You can probably find better price elsewhere.

 

Not going to hurt anything seeing that Audi used to supply the early B5's with a smaller spare tire, plus there are plenty of A4 owners out there running wider wheels/tires in the back which means the front and rear diameter dont exactly match 100%. Not like the front/rear diff sends equal power to both wheels all the time.